Surgery – Radioactive substance applied to body for therapy
Reexamination Certificate
1999-12-27
2001-05-15
O'Connor, Cary (Department: 3736)
Surgery
Radioactive substance applied to body for therapy
C600S003000
Reexamination Certificate
active
06231495
ABSTRACT:
DESCRIPTION
The present invention is related to a radiation emitting, plastic hose for the endovascular therapy of stenoses and restenoses, a method of its preparation and its use.
The expansion of vessels and vascular systems, respectively, which are constricted or closed by tissue proliferations and/or deposits by means of an appropriate balloon catheter, abbreviated PTCA, is one of the possible forms of therapy for treating an angiostenosis or a vascular occlusion (infarct or thrombosis). It is known from results of treating stenoses by conventional, i.e. non-radioactive therapy, that up to 50% of all patients treated in this manner will suffer again within a short time from a vascular occlusion, that is, from a restenosis which makes renewed measures necessary. So-called stents of various materials are used as a supporting measure which are used quasi as support for the expanded vessel. However, it turns out that even this support is often not capable of preventing restenoses. Therefore, various attempts, from the treating of the vessels with medicaments inhibiting cell growth to the use of radioactive stents, are known for the solution of this problem. Experiments with radioactive stents and radioactive balloon catheters used with the object of reducing restenoses have been shown the therapeutic effectiveness of radioactivity.
The disadvantage of radioactive stents can be found in their grid like structure. This structure results on the one hand in a non-uniform irradiation of the surrounding tissue. On the other hand, such stents remain permanently in the body so that a rather long-term radioactive irradiation and therewith a higher integral radiation dosage must be accepted than is necessary.
In order to avoid these disadvantages, devices have been developed which radioactively irradiate the vascular section to be treated only for a few minutes to a few hours. This is achieved by applying the appropiate radiation dosage together with the balloon catheter used for the angioplasty. U.S. Pat. No. 5,213,561 discloses a balloon catheter with a radioactive guide wire. Such a solution has the disadvantage that the radioactivity is not released directly at the tissue to be treated and, in addition, is also screened by the balloon. For this reason either &bgr;-emitters in very high activities or &ggr;-emitters are used in such devices. Both are disadvantageous, since the activities should be held as low as possible. Further, &ggr;-radiation penetrates even into rather low-lying tissue layers which should actually not be irradiated. In addition, &ggr;-radiation is absorbed considerably more poorly than &bgr;-radiation and, therefore, exhibits a lower therapeutic action. Moreover, the use of high activities or the use of &ggr;-emitters results in a significant technical and financial expense for the appropriate safety measures, that is, screenings for the personnel, etc. A further disadvantage is to be found in the very difficult centering of the radioactive guide wire. This centering within the catheter balloon must be exactly assured in order to achieve a uniform irradiation of the vascular section concerned, since otherwise the efficiency of this intervention becomes less, as already described for stents.
It has furthermore been suggested that a radioactive liquid be filled into a special catheter and used as a source for the radioactive radiation, which radioactivity is brought in this manner to the location to be treated. In addition to the disadvantages already cited above caused by the screening of the radioactive source by the balloon skin, this procedure involves other disadvantages which reside in particular in the poorer ability to be manipulated (e.g. leakages, spilling of the liquid, etc.) and basically represent a greater risk in comparison to a solid radioactive source.
A further possibility is constituted by the fastening of radioactive materials or isotopes to the balloon surface. U.S. Pat. No. 5,302,168 describes the fastening of radioactive strips to the balloon skin. However, no statements about the type of fastening or the layer thickness can be determined, so that a permanent adhesion of these strips to the surface is possibly not present here. Finally, even this solution has the disadvantage that the tissue is not uniformly irradiated.
The radioactive balloon catheter described in DE 195 01 154 represents an advance over the solutions already discussed. With respect to DE 195 01 154, the radioactivity is applied permanently in the form of nuclides in, to or on the balloon wall, that is, permanently connected to this wall and forms a homogeneous distribution of the radioactivity there, which is important for a high therapeutic efficiency. However, there are also problems in this instance, particularly with respect to the manufacture of these catheters. From the material-pro-cessing standpoint it is very expensive to first produce the catheter with the balloon, then to dope or coat the balloon radioactively and only then to sterilize it. Further, the isolated manufacture of a balloon provided with radioactive material and its subsequent insertion into a complete catheter is very difficult to perform from a material-processing standpoint. Methods are also used in the production of radioactive stents which comprise the implantation of radioactive material by the bombardment of metallic stents with the corresponding nuclide. However, in the field of plastics, such methods can result in changes of the plastic-elastic properties with the danger of contamination of the patient. In addition, the corresponding production method is very time-intensive. Moreover, analogously to the production methods of stents, an irradiation of the plastic materials which are doped or provided with a metallic layer in appropiate reactors is excluded. On account of the radiation fluxes (thermal neutron flux, etc.) prevailing in the respective reactors and the temperature conditions, the elastic properties of the plastics would degrade and would thus no longer be suitable for use.
Moreover, procedures which describe an application of the radioactive source to the outside of the catheter balloon without a covalent chemical bond of the particular radioactive material involve the risk of so called “Teachings”. This signifies a leaching out of the components which have been added to the balloon from the balloon skin and the associated risk of contamination of the patient.
Also, the application of a layer with a polymeric film which can be cross-linked by light and is compounded with radioisotopes is not uncritical, because it is necessary to produce an elasticity which is comparable to the balloon wall, the elasticity and tensile resistance of which must not be influenced by the introduction of softeners.
The problems presented show that there is a great need in the area of the endovascular therapy of stenoses for a device which is simple to manipulate and makes possible the efficient and reliable use of radioactive radiation, especially the use of &bgr;-radiation, which is therapeutically considerably more effective and simpler to manage. Therefore, the technical problem underlying the present invention is to provide a device which permits a homogeneous and efficient endovascular therapy, preferably radiotherapy, before, during and after a balloon dilation and which does not have the disadvantages cited above, as well as a method of its production, wherein the production of this device should be able to take place separately from the production of the catheter for reasons of cost and also on account of the strict legal regulations with respect to the handling of radioactive substances.
The solution to the afore-mentioned problem is achieved by the embodiments characterized in the claims. In particular, there is provided a radiation emitting, elastic hose for the endovascular therapy composed of at least a polymeric binder comprising at least one elastomer, wherein at least a radioisotope or a radioisotope-containing compound or a combination thereof is incorporated into the polymeric binde
McDermott & Will & Emery
O'Connor Cary
Szmal Brian
Universitat Karlsruhe
LandOfFree
Radiation emitting, elastic hose for the endovascular therapy does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Radiation emitting, elastic hose for the endovascular therapy, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Radiation emitting, elastic hose for the endovascular therapy will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2564183